1. Field of the Invention
The present invention relates to an intermediate multilayer wiring board product (i.e., an intermediate product of a multilayer wiring board manufacturing method, or an intermediate product of a multilayer wiring board) including a product forming region in which a plurality of product portions to become products are arranged along a planar direction and a frame portion surrounding the product forming region, as well as to a method for manufacturing a multilayer wiring board obtained from an intermediate product of a multilayer wiring board.
2. Description of Related Art
As one technique for efficiently manufacturing a wiring board, a plurality of wiring board products are obtained from one intermediate wiring board product. Such intermediate product usually includes: a product forming region in which a plurality of product portions that are to become products are arranged along a direction of a plane; and a frame portion surrounding the product forming region. A product-side conductor layer is formed on surfaces of product portions that are to become products, whereas no conductor layer is formed on the surface of the frame portion that is not to become a product. In recent years, a dummy conductor layer (a frame-side conductor layer) made by plating is provided in a solid pattern on the surface of the frame portion for the purpose of suppressing warping (also referred to as “warpage”). Moreover, another wiring board includes a frame-side conductor layer having a meshed pattern rather than in a solid pattern (see, for example, JP-A-2007-180212).
As an intermediate product of the wiring board, an intermediate multilayer wiring board product of a has been put into practical use. The intermediate multilayer wiring board product includes a core board and a build-up layer formed on each of front and back surfaces of the core board. In the intermediate multilayer wiring board product, for example, a resin board (such as a glass epoxy board, and the like) made by impregnating reinforced fiber with resin is used for the core board. The build-up layer is made by alternately stacking a resin insulating layer and a conductor layer on each of the front and back surfaces of the core board, thereby utilizing the rigidity of the core board. In short, the core board reinforces the intermediate multilayer wiring board product and has a thickness largely thicker than the build-up layer. The intermediate product includes an interconnection (specifically a through hole conductor and the like) penetrating the core board for establishing electrical connection between build-up layers formed on the front surface and the back surface of the core board. The intermediate product allows a semiconductor integrated circuit element (an IC chip), such as a microprocessor of a computer and the like, to be mounted thereon.
Recently, as semiconductor integrated circuit elements become faster, signal frequencies used in the elements increase (i.e., become higher). Under these circumstances, the interconnection penetrating through the core board acts as a large inductance, which in turn leads to the occurrence of transmission losses in the high-frequency signals and faulty circuit operations. Thus, a increasing the speed of the semiconductor integrated circuit elements may be hindered. In view of this disadvantage, a coreless multilayer wiring board (i.e., a wiring board not having any core board) is proposed (see, for example, JP-B-3664720). Since a relatively thick core board is omitted from the coreless wiring board, the entire length of the interconnection is shortened. Consequently, transmission losses in high frequency signals are reduced, and the semiconductor integrated circuit elements can be operated at high speed.